This invention relates to a therapeutic gas flow meter and, in particular to a flow meter which monitors the flow setting and flow adjustments made by a patient or user of therapeutic gas.
Generally, a patient with a pulmonary breathing disorder or oxygen deficiency is required to breath oxygen provided from a source of oxygen to increase the level, or amount of oxygen they breath in from the atmosphere. The patient is given a prescription that indicates the concentration of oxygen, the flow or volume requirement of oxygen, and the use of the oxygen, for example, the hours per day of oxygen delivery. In some cases, the prescription will include the precise hours of the day the patient is to receive the oxygen therapy. For example the patient's prescription may call for two liters of oxygen per minute for two hours during the day and eight hours at night. Or, in some cases, the prescription may call for four liters of oxygen per minute for twenty-four hours a day. Usually the prescription is based upon oxygen requirements established in a controlled setting, such as at a hospital during hospitalization. The prescription is continued at home after the patient is discharged from the hospital. Delivery of oxygen therapy at home should correspond to the prescription developed in the hospital. Failure to comply with the prescription could be harmful to the patient or less beneficial than planned.
Oxygen concentrators have been developed and commercialized to provide the delivery of near pure oxygen to the individual patient to satisfy medical needs. These concentrators can be small and portable. However, once the patient leaves the controlled setting of the hospital, it is difficult to monitor the patient's use of the oxygen to ensure that he is complying with the prescription. An important part of a patient's therapeutic gas prescription is the flow amount or rate. Thus, it is important to know at which level the patient has set his therapeutic gas meter and equally important to know when and to what amount an adjustment is made.
The preferred therapeutic gas source generally is an oxygen concentrator. Other therapeutic gas sources can of course be used. The gas source normally uses an adjustable flow meter having a ball indicator so that the user can read the flow rate. Two common flow meters found in oxygen concentrators are those manufactured by Key Instruments of Trevose, Pa., under Part #FO43, and by Dwyer Instruments of Michigan City, Ind., under Part #59-700360-00. A typical flow meter 1 is shown in FIGS. 1 and 2. The flow meter 1 includes a meter body 3 having an inlet port 5, and outlet port 7, and a Thorpe Tube 9 between the inlet and outlet through which the gas flows. An indicator ball 11 floats in the Thorpe Tube 9 and is elevated or floated in the Thorpe Tube by the flow of gas through the tube 9. The level to which the ball 11 is raised is indicative of the flow rate of gas through the meter. An indicating scale 13 is provided to allow a user to read the flow rate. A user adjustable metering valve 15 is operated by a knob 17 to alter the flow through the meter. Typically, the valve 15 is a needle valve, and includes a needle portion 19 which extends forwardly of a shaft 20 and into the throat 21 of the outlet 7. The valve shaft is threaded, as at 23. The threads 23 are received in an internally threaded boss 25. An O-ring 27 is provided to prevent gas from escaping out through the boss. Thus, as can be appreciated, by rotating the knob 17, the needle 19 moves axially to be inserted into, or pulled away from, the throat 21, to open or close the outlet 7.
Operation of this type of flow meter is simplistic and well known in the art. Therapeutic gas enters inlet port 5 travels through Thorpe Tube 9 causing the indicator ball 11 to rise to a level which is proportional to the amount of therapeutic gas flow which exits at the outlet port 7. When the user desires to control the flow of therapeutic gas the patient adjusts the user adjustable metering valve knob 17 alters the degree to which the throat 21 is open, to decrease or increase the therapeutic gas flow to the desired level as indicated by the alignment of the indicator ball 11 on the indicating scale 13. Typically the user rotates the user adjustable metering valve knob 17, in a clockwise direction to restrict the flow of therapeutic gas to a lesser amount and likewise the user may adjust the metering valve knob 17 counter-clockwise for a greater amount of therapeutic gas flow.
Flow information is normally only available by reading the ball indicator on the flow meter. When it is desired to obtain flow information via electronic means an electronic flow sensing means must be added to the meter. Flow sensing means and the use of flow sensors to monitor the flow of a gas through a meter are known. However, we know of no sensors which monitor the setting of the meter. When using an oxygen concentrator, it may be necessary to monitor the valve setting independently of the flow rate. In these cases it is necessary to not only monitor flow settings but also to log into memory flow setting data to communicate this data to a care giver.